Working with Adjacent Angles

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  • 0:01 Adjacent Angles
  • 0:43 How to Identify
  • 1:43 Sum of Angles
  • 2:22 Finding a Missing Angle
  • 3:33 Lesson Summary
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Lesson Transcript
Instructor: Yuanxin (Amy) Yang Alcocer

Amy has a master's degree in secondary education and has taught math at a public charter high school.

After watching this video lesson, you will know how to work with adjacent angles. You will know how to identify them, how to find the sum of the adjacent angles and how to find the measure of a missing angle.

Adjacent Angles

Angles are all around us. Knowing how to work with angles helps you know how to answer test problems, and it will help you to solve everyday problems. Take a look at a pizza slice. It looks delicious with the cheese all melted on top of the pepperoni slices! Before you take that bite, look at the tip of your pizza slice. That tip can actually represent an angle in math. If you draw just the sides of your pizza from the tip, you will have your angle. Put two pizza slices next to each, and you will have what are called adjacent angles. A pair of adjacent angles are angles that are next to each other.

adjacent angles

We will focus on adjacent angles on for this lesson.

How to Identify Adjacent Angles

First, let's talk about identifying adjacent angles. How do you know whether two angles are adjacent angles?

adjacent angles

Take a look at these three angles. If you picture these three angles as three pizza slices, then your adjacent angles are those pizza slices that are next to each other. If they are not next to each other, then they are not adjacent. So, angles two and three are adjacent, as are angles one and two. But angles one and three are not adjacent because they are not next to each other. How about these angles?

adjacent angles

Which would you say are adjacent? One and two are adjacent, two and three are adjacent, three and four are adjacent and four and one are adjacent. What about angles one and three? Are they adjacent? No, they are not because they are not next to each other. Now that you know how to identify adjacent angles, let's try working with their angle measurements.

Sum of Angles

Sometimes, you will be given two adjacent angles and asked to find the sum of the angles. In this case, you will usually know the measure of each of your angles. For example, you might be given a problem like this.

adjacent angles

The problem might ask you to find the sum of these angles. How do you go about answering this question? Well, you know what sum means: it means to add. So if you need to add up these angles, then your answer can be found by adding up the angle measurements that are given. You see that one angle measures 25 degrees, and the adjacent angle measures 35 degrees. The sum of these angles then is 25 + 35 = 60. The answer is 60 degrees.

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